No slits allowed - What's the problem with QM

There 's a great deal more to QM than the two (or more) slit experiment. So, I'm still interested in problems with QM, but within the context of QM dealing with many phenomena. So anybody got problems with theories/ experiments
like:

Superconductivity

Semiconductors

Lasers & Glauber's coherent state formalism

Rosenbluth or Rutherford cross sections & radiative corrections

Feynman/Dirac path integral formalism

QM of non-Abelian gauge theories

Electro-weak theory

Models of the nucleus

Many body theory

Non-equilibrium statistical mechanics

and on and on.

To me, this is a small list of the real stuff of QM.

If there are QM problems, how do they show up in issues like those in the above list? No slits allowed -- although crystal lattices are fair game